The Army has stopped live firing exercises on Salisbury Plain after smoke from a fire spread across the West Country.
The plume affected large parts of west Wiltshire and travelled as far away as Bath in Somerset in the past 24 hours.
The MOD's Principal Training Officer for the South West, Lieutenant Colonel Tim Jalland, said that the fire has been burning for two weeks but cannot be tackled because it is within a live firing range.
The MoD said the fire was not a risk to property but admitted the smoke was "very unpleasant".
The Ministry of Defence said there were fire wardens monitoring the site and firefighters could be brought in if flames spread outside the impact zone.
Live firing on Salisbury Plain has been stopped until further notice.
Dorset and Wiltshire Fire and Rescue Service received dozens of 999 calls overnight, with firefighters attending incidents of alarm systems being triggered by smoke on multiple occasions.
Public Health England has advised residents to stay indoors and keep their doors and windows closed.
Drivers should also keep windows shut and switch on air conditioning systems to recycle or recirculate air.